Dataset Information

An unusual xylan in Arabidopsis primary cell walls is synthesised by GUX3, IRX9L, IRX10L and IRX14.

ABSTRACT: Xylan is a crucial component of many plant primary and secondary cell walls. However, the structure and function of xylan in the dicotyledon primary cell wall is not well understood. Here, we characterized a xylan that is specific to tissues enriched in Arabidopsis primary cell walls. Unlike previously described xylans, this xylan carries a pentose linked 1-2 to the α-1,2-d-glucuronic acid (GlcA) side chains on the β-1,4-Xyl backbone. The frequent and precisely regular spacing of GlcA substitutions every six xylosyl residues along the backbone is also unlike that previously observed in secondary cell wall xylan. Molecular genetics, in vitro assays, and expression data suggest that IRX9L, IRX10L and IRX14 are required for xylan backbone synthesis in primary cell wall synthesising tissues. IRX9 and IRX10 are not involved in the primary cell wall xylan synthesis but are functionally exchangeable with IRX9L and IRX10L. GUX3 is the only glucuronyltransferase required for the addition of the GlcA decorations on the xylan. The differences in xylan structure in primary versus secondary cell walls might reflect the different roles in cross-linking and interaction with other cell wall components.

SUBMITTER: Mortimer JC

PROVIDER: S-EPMC4528235 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature

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An unusual xylan in Arabidopsis primary cell walls is synthesised by GUX3, IRX9L, IRX10L and IRX14.

Mortimer Jenny C JC Faria-Blanc Nuno N Yu Xiaolan X Tryfona Theodora T Sorieul Mathias M Ng Yao Z YZ Zhang Zhinong Z Stott Katherine K Anders Nadine N Dupree Paul P

The Plant journal : for cell and molecular biology 20150625 3

Xylan is a crucial component of many plant primary and secondary cell walls. However, the structure and function of xylan in the dicotyledon primary cell wall is not well understood. Here, we characterized a xylan that is specific to tissues enriched in Arabidopsis primary cell walls. Unlike previously described xylans, this xylan carries a pentose linked 1-2 to the α-1,2-d-glucuronic acid (GlcA) side chains on the β-1,4-Xyl backbone. The frequent and precisely regular spacing of GlcA substituti ...[more]

PMID: 26043357

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Project description:BackgroundXylan is a major hemicellulosic component in the cell walls of higher plants especially in the secondary walls of vascular cells which are playing important roles in physiological processes and overall mechanical strength. Being the second most abundant cell wall polymer after cellulose, xylan is an abundant non-cellulosic carbohydrate constituent of plant biomass. Xylan structures have been demonstrated to contribute to plant biomass recalcitrance during bioenergy applications. A critical understanding of xylan composition, structure, and biosynthesis in developing plant stems will allow an increased understanding of how cell walls are put together in this organ in a basic research, and, in applied research, will improve strategies in xylan engineering to reduce biomass recalcitrance for economically feasible biofuel production.MethodsWe describe an approach to enable the monitoring of xylan epitope structures in cell walls during the stem maturation process in Arabidopsis. The technique integrates glycome profiling, an in vitro immunoanalytical platform, and in situ immunolocalisation to provide comprehensive details on the presence, relative abundances, and dynamics with which diverse xylan epitope structures are integrated to the cell walls throughout the stem maturation process.ResultsOur experimental results and the supporting in silico analysis demonstrated that xylan deposition in stems occurs early on in stem development; however, xylan epitope types (representing substituted and unsubstituted regions on xylan backbone made of β-(1,4)-linked xylose residues) and the strength of their integration into the final wall structure vary during stem maturation.ConclusionsOur novel approach thus provides a method to comprehensively survey the differences in xylan epitope patterning and deposition occurring in stem development and thereby providing a robust tool for characterising altered xylan integration patterns in cell walls during the stem maturation process in diverse plant cell wall biosynthetic mutants. Our findings also suggest that this approach could rapidly and reliably delineate xylan deposition patterns in the cell walls of plants belonging to diverse phylogenetic classes providing novel insights into the functional roles of xylans in overall growth and development.

Project description:Plant biomass represents an abundant and increasingly important natural resource and it mainly consists of a number of cell types that have undergone extensive secondary cell wall (SCW) formation. These cell types are abundant in the stems of Arabidopsis, a well-studied model system for hardwood, the wood of eudicot plants. The main constituents of hardwood include cellulose, lignin, and xylan, the latter in the form of glucuronoxylan (GX). The binding of GX to cellulose in the eudicot SCW represents one of the best-understood molecular interactions within plant cell walls. The evenly spaced acetylation and 4-O-methyl glucuronic acid (MeGlcA) substitutions of the xylan polymer backbone facilitates binding in a linear two-fold screw conformation to the hydrophilic side of cellulose and signifies a high level of molecular specificity. However, the wider implications of GX-cellulose interactions for cellulose network formation and SCW architecture have remained less explored. In this study, we seek to expand our knowledge on this by characterizing the cellulose microfibril organization in three well-characterized GX mutants. The selected mutants display a range of GX deficiency from mild to severe, with findings indicating even the weakest mutant having significant perturbations of the cellulose network, as visualized by both scanning electron microscopy (SEM) and atomic force microscopy (AFM). We show by image analysis that microfibril width is increased by as much as three times in the severe mutants compared to the wild type and that the degree of directional dispersion of the fibrils is approximately doubled in all the three mutants. Further, we find that these changes correlate with both altered nanomechanical properties of the SCW, as observed by AFM, and with increases in enzymatic hydrolysis. Results from this study indicate the critical role that normal GX composition has on cellulose bundle formation and cellulose organization as a whole within the SCWs.

Dataset Information

An unusual xylan in Arabidopsis primary cell walls is synthesised by GUX3, IRX9L, IRX10L and IRX14.

Publications

An unusual xylan in Arabidopsis primary cell walls is synthesised by GUX3, IRX9L, IRX10L and IRX14.

Similar Datasets

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